We've already gotten word of a few Windows 7 upgrade plans, but it looks like things are now really starting to get fleshed out, even if nothing's quite official just yet. According to PC World, at least some PC vendors will be kicking off a coupon program on June 26th, which will let folks that buy premium versions of Windows Vista upgrade to Windows 7 when it rolls out this fall. As you might expect, however, things won't be completely consistent across the board, and it won't be a free upgrade in every case either. That's partly because vendors will reportedly have to shell out between $9 and $15 per PC to include the upgrade coupon, although at least three unnamed Taiwanese PC makers will apparently be taking a hit on that cost and offering a free upgrade coupon to anyone that buys a laptop or desktop loaded with Vista Home Premium, Ultimate or Business. HP is also said to be participating in the upgrade program, although it says it won't be revealing any details until Microsoft itself officially announces the start date for the program.